184 
ME. G. GOEE ON HYDEOELUOEIC ACID. 
the slight excess of silver found in this determination. The amount of fluorine in the 
flltrate was determined by means of a solution of calcium salt in the usual manner ; it 
gave 4-40 grains of fluoride of calcium = 2T436 grains of fluorine, the quantity required 
to complete the weight being 2’24 grains. In my hands this process of determining the 
amount of fluorine has not hitherto yielded very accurate results. — Received January 9, 
1869.]* 
These results, combined with the foregoing experiments on molecular volume, agree 
with the conclusion that a volume of hydrogen weighing 1 unites with 19 parts by 
weight of fluorine to form 2 volumes of hydrofluoric acid, and that the specific gravity 
of gaseous anhydrous hydrofluoric acid is ten times the amount of that of hydrogen. 
The acid vapour obtained by heating fluoride of silver in the closed vessel of hydrogen 
over mercury, as already described, was transferred to glass vessels over mercury ; it was 
colourless, and quite transparent ; it did not corrode the glass vessels or render them 
dim in the slightest degree during several weeks, provided moisture was entirely absent, 
but if there was the slightest trace of damp present the surface of the glass soon lost its 
brightness. A fragment of ice introduced into the gas instantly caused the surface of the 
glass near it to become corroded and opaque white. The vapour of hydrofluoric acid 
escaping at any minute orifice from a vessel of the dry acid, condenses moisture rapidly 
upon the contiguous parts of the vessel. 
Fremy sought for oxygen in the anhydrous acid, but was unable to find anyf. Sir 
H. Davy also, who prepared his acid by distilling fluor-spar with sulphuric acid contain- 
ing not more than 1 equivalent of water, could find no oxygen in it, either by electro 
lysis, or by neutralizing it with gaseous ammonia; but when the sulphuric acid he 
employed contained more than 1 equivalent of water, he found water in the hydro- 
fluoric acid. The acid obtained in my experiments also I consider to be destitute of 
oxygen, not only from the results obtained in the various analyses and experiments 
already described, but also, 1st, because the double fluoride of hydrogen and potassium 
from which the acid was prepared, when fused and electrolyzed with platinum electrodes, 
evolved abundance of inflammable gas at the cathode, but yielded no gas at the anode, 
although oxides are by electrolysis decomposed before fluorides ; 2nd, the electrolysis 
of the anhydrous acid with platinum electrodes 'yielded no odour of ozone, whereas 
hydrofluoric acid containing various percentages of water evolved that odour strongly 
(see page 199) ; 3rd, the properties of hydrofluoric acid prepared by heating pure 
fluoride of silver in pure hydrogen (see pages 181 & 182) agreed in properties, as far as 
those properties were ascertained, with the acid obtained from the double salt ; and 
4th, because two volumes of gaseous anhydrous hydrofluoric acid were produced by the 
reaction of one volume of hydrogen upon its equivalent of fluoride of silver, whereas if 
* Note, added May 25, 1869. I have since, by repeated and more accurate analyses, confirmed the compo- 
sition of the recently fused salt to be wholly silver and fluorine, with a small quantity of enclosed metallic 
silver. — G. G. 
t Comptes Eendus, February 27th, 1854. 
